Ceramic phase change container

ABSTRACT

An article for holding foodstuff. The article comprises a receptacle (4) having a wall with an inner surface for holding the foodstuff and an opposite outer surface. The wall is formed of a first material, such as a ceramic material, having a first thermal conductivity. The articles also has a shell (1; 5) spaced apart from the outer surface of the receptacle such as to define an interstitial chamber (2, 3) between the shell and the outer surface of the receptacle. The shell is at least partially formed of a ceramic material with a second thermal conductivity. Within the interstitial chamber, there is disposed a phase change material which abuts with at least the outer surface of the wall of the receptacle. The first thermal conductivity being greater than the second thermal conductivity, so as to allow for heat transfer through the wall to the phase change material, which will accumulate the heat.

FIELD

The invention relates to a container that retains temperature at a preferred level. In some embodiments, the present invention concerns articles for holding hot foodstuff, such as hot liquids, while rapidly cooling them from hot to warm and then maintaining the liquid in the warm range for an extended period of time. Other embodiments relate to articles for increasing temperature of a foodstuff or for cooling a foodstuff to a temperature below the ambient.

BACKGROUND

Solutions for retaining the heat of a substance in a container have been searched and tried for decades. These solutions include examples of keeping bath water or a drink warm for a longer time period. Methods of retaining the heat have included insulation, use of electricity and use of phase change materials.

Insulation is able to effectively slow down the cooling process, but as a drawback, it takes a long time to reach the preferred temperature. Once the preferred temperature has been reached, the temperature will drop at almost the same pace.

Electricity enables the retainment of heat at the preferred temperature. However, cords limit the container's portability and batteries need to be replaced or recharged.

The use of a phase change material allows for an autonomous container that retains heat at the preferred temperature. The phase change material melts from a solid to a liquid when the temperature is too high. This causes the temperature to quickly fall. As the phase changes, the phase change material absorbs a relatively large amount of energy as latent heat. When the temperature in the container reaches the predetermined temperature, which is also close to the preferred temperature, at which the phase change material solidifies, the phase change material releases the previously captured latent heat. This results in the container maintaining the preferred temperature for an extended period of time. Phase change material can be used to rapidly cool or heat and to keep hot or cool.

There are a number of patents and products which relate to the use of phase change material to retain heat in a container. For example, the U.S. Pat. No. 2,876,634A from 1954 describes drinking vessels and saucers that keep liquid cool or hot using phase change materials.

Phase change materials have been used in containers, such as cups. For example, this is described in U.S. Pat. No. 2,876,634A.

On the market, there are products as described in patent U.S. Pat. No. 7,934,537 B2, viz. receptacles for rapidly lowering the temperature of a liquid to a suitable temperature for an extended period of time. An example of such a product is a stainless steel travel mug. The phase change material lies in a cavity in between the inner and outer wall of the mug.

The usage of phase change materials is useful in many applications, such as mugs, baths, and baby bottles, enabling a safe and pleasant temperature.

Although phase change materials have been used in containers such as cups, the material choice for the container has been limited; the inner receptacle needs to be made of a food grade material, it needs to be capable of transferring heat and it needs to be mass producible.

In order to make a phase change material vessel work (such as achieving adequate keep-hot or keep-cold functionality or/and allow the vessel to charge up thermal energy from e.g. hot or cold beverage or hot or cold food), the material in contact with the phase change material needs to have very good thermal conductivity. However, some phase change materials, especially phase change materials with good volumetric heat capacity, can be corrosive towards different metals (for example carbon steel, iron, aluminum or copper or their alloys). Some grades of stainless steel can endure some phase change materials without corrosion, but the low thermal conductivity of such materials can be a limiting factor. Also metallic vessels can possess other limitations such as microwave incompatibility, food safety issues (e.g. leaching of metal or metal ions in acidic or alkaline environment), and esthetic factors—traditionally cups and saucers have been made from ceramic.

There is a need for providing articles for holding and containing foodstuff which employ esthetically attractive, food grade, microwave compatible and corrosion resistant materials that allow for efficient heat transfer to the substance inside of the container, and for insulation of heat from the container to the outside.

SUMMARY OF THE INVENTION

It is an aim of the invention to remove at least a part of the problems relating to the known technical solutions and to provide an article made from materials having different thermal conductivities and forming between them a space for containing a phase changing material for latently storing of heat. The heat, when released from the phase change material, will then assist in maintaining the foodstuff held in contact with one material of higher thermal conductivity at a wanted temperature range when used.

The article comprises of a receptacle having a wall with an inner surface for holding the foodstuff and an opposite outer surface. The wall is formed of a first ceramic material having a first thermal conductivity to allow for heat transfer through the wall. It has a shell spaced apart from the outer surface of the receptacle such as to define an interstitial chamber between the shell and the outer surface of the receptacle. The shell is at least partially formed of a second ceramic material and has a second thermal conductivity.

There is a phase change material disposed within the interstitial chamber and abutting at least the outer surface of the wall of the receptacle. The first thermal conductivity is greater than the second thermal conductivity to allow for the accumulation of heat by the phase change material.

More specifically, the articles according to the present invention are characterized by what is stated in the characterizing part of claim 1. The use according to the present invention is characterized by what is stated in claim 18.

Considerable advantages are obtained by the invention. Thus, the present articles for example in the form of cups and mugs and other containers for holding and containing aqueous liquids, such as hot beverages, e.g. coffee or tea, efficiently use latent heat storage materials to absorb extra thermal energy from the beverage, and then release the energy at drinking temperature, thus keeping the beverage hot for longer at the suitable drinking temperature.

As tests show and as will appear from FIG. 3, compared with regular drinking mugs of equal volume, the time window for keeping hot beverages at a temperature which still is acceptable for a hot beverage, is about 50 to 300% longer for the present articles that are presented in FIG. 1.

The present articles can also be used for cooling foodstuff below ambient temperature and for maintaining the foodstuff at such temperatures for extended periods of time.

The present article can also be used for raising the temperature of foodstuff above its initial temperature and maintain the temperature of the foodstuff at such a temperature.

In preferred embodiments, the present articles are produced mainly or exclusively from ceramic materials which will give the articles an attractive appearance. Additionally, use of ceramics will mean better food safety at elevated temperatures and microwave compatibility. Ceramic materials are dishwasher safe.

Further features and advantages will appear from the following disclosure of embodiments of the present technology.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows in side-view a partial cross-section of the wall of a container according to one embodiment;

FIG. 2 shows in side-view a detail of the lip portion of a sidewall;

FIG. 3 shows the temperature as a function of time of the content inside one 300 ml ceramic mug according to an embodiment of the present invention, compared with a reference mug;

FIG. 4 shows in side-view the cross-section of a mug according to one embodiment; and

FIG. 5 shows in side-view the cross-section of a plate according to one embodiment.

EMBODIMENTS

The solution described in the present invention falls under the use of phase change materials.

The present technology relates generally to liquid receptacles or containers and more specifically to receptacles which are in thermal contact with phase change materials for allowing heat flux between the content of the receptacles and the phase change materials.

Embodiments of the present technology address the need for cooling a hot liquid to a warm range and then maintaining the fluid in the warm range for an extended period. Thus, for example, articles for containing or holding foodstuff are provided which rapidly lower the temperature of food and beverages, such as liquids, to a warm range suitable for human contact and then maintain the liquid in the warm range for an extended period of time.

In other embodiments, the present invention concerns articles for cooling foodstuff to a temperature below the ambient and maintaining the temperature in such a range for an extended period of time.

In still further embodiments, the present invention concerns articles for raising the temperature of foodstuff to a preselected temperature higher than that of the original foodstuff and even higher than that of the ambient.

One embodiment comprises an article for holding foodstuff, such as aqueous foodstuff, comprising a receptacle having a wall with an inner surface for holding the foodstuff and an opposite outer surface, the wall being formed of a first material having a first thermal conductivity to allow for heat transfer through the wall. The article also comprises a shell spaced apart from the outer surface of the receptacle such as to define an interstitial chamber between the shell and the outer surface of the receptacle, the shell being at least partially formed of a ceramic material having a second thermal conductivity. Within the interstitial chamber there is disposed a phase change material. The phase change material abuts with at least the outer surface of the wall of the receptacle.

One embodiment comprises an article similar to the above mentioned that has a bottom comprised of a polymeric material which is placed on the opposite side to the lower end of the receptacle.

The thermal conductivity of the first material is being greater than the thermal conductivity of the second material. Typically, the thermal conductivity is at least 20%, in particular at least 50%, preferably at least 100%, advantageously at least 250%, and for example at least 500% greater of the first material than of the second material.

One embodiment comprises a receptacle having a side wall with a lower end and an open upper end. A bottom wall closes off the lower end of the side wall. The side wall has an inner surface and a spaced outer surface. An interstitial chamber is defined by the space between the inner and outer surfaces. An insulation layer is disposed at least partially between the chamber and the outer surface of the receptacle. A phase change material at least partially fills the chamber.

In some of the above embodiments, the phase change material regeneratively absorbs thermal energy from a hot liquid in the receptacle thereby rapidly lowering the temperature of the liquid and then the material releases the thermal energy back to the liquid to maintain the temperature of the liquid.

In other embodiments, articles are provided for increasing temperature of a foodstuff or for cooling a foodstuff to a temperature below the ambient by releasing or absorbing thermal energy from the phase change material similarly as to the above mentioned embodiment.

In embodiments, the first material comprises particular, at least partially, ceramic materials, in the following referred to as “thermally conductive ceramics”.

In the present context, the term “ceramic” comprises inorganic materials that are pure or mixture of metal or metalloid oxides or nitrides ceramics that can be fully densified or partially densified by sintering or fusing.

In addition the ceramics described in the present context can also include fully amorphous or partially amorphous or semi-crystalline form of metal or metalloid oxides or nitrides.

Ceramic materials can include porcelain, stoneware, earthenware, bone china, technical porcelain, high alumina porcelain, other traditional pottery materials, aluminosilicate glass, fused silica glass, boronsilicate glass, soda-lime glass, and other glasses that are doped with metal oxide or mixture of metal oxides. Technical ceramics include pure or non-pure aluminium oxide, mullite, zirconia oxide or stabilized zirconia oxide compositions, aluminium nitride, titanium oxides and its mixtures.

The ceramic materials shall be glaze-able or glass coat-able or frit bondable.

The ceramics can be partially coated with glaze or enamel to improve esthetics and easiness to clean.

The first material can, in addition to ceramics of the above kind, also comprise combinations of ceramics and other materials, such as polymeric materials, in particular thermoplastics, elastomers and silicone materials. Typically, a majority (i.e. 50% or more by weight) of the first material is a ceramic material.

However if the whole container is made from thermally conductive ceramics, the heat transfer to or from the air will be accelerated, thus shortening keep-hot or keep-cold duration, and it would make the whole vessel very hot for handling. Therefore the current invention uses the thermally conductive ceramics that are bonded with thermally less conductive ceramics.

The second material comprises a “thermally less conductive material”. The thermally less conductive material can be selected from ceramics and from combination of ceramics and polymeric materials. In the latter case, typically, the second material comprises at least 10% by weight of a ceramic material, for example up 95% by weight.

In one embodiment, the ceramic material forms at least 20% by weight of the second material.

The ceramic part of the thermally less conductive material can be selected from the group of porcelain, stoneware, earthenware, feldspar porcelain, bone china, high alumina porcelain, or other tri-axial porcelain systems.

The advantages of ceramic materials is that the materials are chemically inert, they have good food contact compatibility, they are compatible with microwave heating, they are aesthetic and have a traditional appearance, and typically dish-washer safe. Further, ceramics are corrosion resistant and as heat insulating materials in the outer shell will protect the user from burning hands or lips when used. The present invention retains temperature at preferred level, can store heat energy, can rapidly cool/heat.

In one embodiment, the thermally conductive ceramics used for contact with phase change materials comprises porcelain having a high Al₂O₃ content.

In one embodiment, the thermally conductive ceramics used for contact with phase change materials, in particular the material forming the receptacle is selected from the group of ceramics, metal oxides and metalloid oxides and combinations thereof, for example Al₂O₃, in particular an Al₂O₃ grade having an Al₂O₃ content of 75 to 100% by weight.

In one embodiment, the thermally conductive and thermally less conductive ceramics are bonded together by co-firing, frit bonding, or glass or glaze bonding. Such methods are preferred in view of potential differences in coefficients of thermal expansion of ceramic materials. This will be examined in more detail below.

In one embodiment, the thermally conductive and thermally less conductive ceramics are bonded together by gluing.

In one embodiment the article comprises a vessel primarily for containing liquids, such as a cup, a bowl or bottle, or an article primarily for holding non-liquid foodstuff, such as a saucer, plate, platter or bowl. The term “receptacle” covers any article capable of containing or holding foodstuff, liquid as well as non-liquid, for any of the above uses.

In one embodiment the article wherein the receptacle has an open upper end and closed lower end, wherein the wall interconnects the upper and the lower ends of the receptacle, so as to define a volume.

In one embodiment of the article the shell at least partially laterally surrounds the wall of the receptacle.

In one embodiment the article comprising a plate with typically inclined edges for holding aqueous foodstuff or liquids.

The plate can also be flat, for example a plate with non-inclined edges or simply a planar structure. Such a structure will be useful for holding non-liquid foodstuff. In other embodiments, a flat structure can be used as a heat accumulator, for example for use as a heating plate which can be preheated by placing it in contact with heat, such as hot water or a microwave source, whereby the flat structure will release heat over an extended period of time to any object placed upon it. Similarly, the structure can also be used for storing cold. Examples of structures include mats, table mats, beer mats, coasters and pot coasters.

In one embodiment the article exhibits a receptacle having a wall with first edge portions defining the perimeter of the wall, and a shell has second edge portions defining the perimeter of the shell, said first and second edge portions are being bonded together.

In one embodiment, the ceramic material of the shell is a heat insulating silicate, in particular metal silicate material.

In one embodiment, the article has a shell which consists essentially of ceramic material.

In one embodiment, the article comprises a shell of a ceramic material which laterally surrounds the wall of the receptacle and a polymeric material which forms the bottom of the vessel and which is placed on the opposite side to the lower end of the receptacle.

In one embodiment of the article, the polymeric material which forms the bottom of the vessel is selected from the group of silicone, elastomeric and thermoplastic materials and combinations thereof.

In one embodiment of the article, the wall of the receptacle is sealed to the shell.

“Sealed and “sealing” stands for a bonding of the receptacle to or against the shell so as to reach a bonding therebetween so that no foodstuff, such as liquid, will pass through the sealing during conventional use of the article for holding liquids.

In one embodiment of the article the ceramic material of the inner layer is bonded to the ceramic material of the shell by co-firing, frit bonding or glass or glaze bonding of the ceramics.

In one embodiment the article comprising an elasticity zone disposed within the interstitial chamber on the opposite side of the phase change material with respect to the outer surface of the wall to allow for expansion and contraction of the phase change material within the interstitial chamber under the influence of thermal energy.

In one embodiment, the elasticity zone separates at least a significant portion of the shell and the phase change material.

In one embodiment, the elasticity zone comprises a silicone, elastomer or thermoplastic material or a combination thereof.

In one embodiment, the elasticity zone comprises a gas-filled space.

The elasticity zone will aid in keeping the phase change material constantly in contact with the outer surface of the receptacle for thus ensuring proper heat transfer between the content of the receptacle, i.e. the foodstuff kept in the receptacle, and the phase change material.

FIG. 1 depicts one embodiment of the invention. This is a side-view of a partial cross-section of the wall of a container. The bottom 1 of the container is formed of some polymeric material, preferably selected from the group of silicone and elastomeric materials. The phase change material 2 partially fills the interstitial chamber which is located between the receptacle 4 and the shell 5. An elasticity zone 3 is left between the phase change material 2 and the shell 5. The purpose of the elasticity zone 3 is to allow the expansion and contraction of the phase change material without cracking the ceramic material of either the receptacle or the shell.

FIG. 2 shows a side-view detail of the lip portion of a sidewall to one embodiment of the invention. The detailed view shows that the lip portion of the sidewall is the same heat insulating ceramic material as the shell 5. This way the mug does not burn the users lip as they drink from it. This figure also shows the seam where the bonding of the two ceramic materials of the receptacle 4 and the shell 5 takes place.

FIG. 3 shows the temperature as a function of time of the content inside one 300 ml ceramic mug according to the embodiment similar to the one presented in FIG. 1 of the invention, compared to a reference mug.

The graph presents the upper limit of 62° C. and lower limit 48° C. that is the ideal temperature range of a warm beverage.

As will appear, the beverage in the reference mug stays within said temperature range from minute 12 to minute 29 and the beverage in the mug presented in one embodiment of this invention is within said temperature range from minutes 9 to 37. While cooling the beverage quicker to the wanted temperature the mug presented in this invention also keeps the beverage within the wanted temperature range for a longer period of time.

FIG. 4 depicts one embodiment of the invention. The drawing shows in side-view a cross-section of a mug where the ceramic outer shell 15 is partially replaced by a plastic shell 17. Using plastic reduces the weight of the mug, increases insulation and decreases the heat capacity. The holder 16 for the phase change material 12 is an elastic or non-elastic band that keeps the phase change material closer to the side of the mug. This enables optimized distribution of the phase change material against the outer surface of the receptacle.

FIG. 5 shows in side-view of a cross-section of a plate according to one embodiment of the invention. As in the previously presented embodiments, this embodiment also has a bottom 21, phase change material 22, a receptacle 24 and a shell 25.

This figure shows a spiked structure of the receptacle and phase change material. This structure is used since the spiked structure will give an increased area in the interface between the receptacle and the phase change material which means better heat exchange.

In the embodiments shown in FIGS. 1, 2, 4 and 5, the bonding between the edges of the receptacles, 4, 14 and 24, and the corresponding (abutting) edges of the shell, 5, 15 and 25, are provided by frit bonding or glaze or glass bonding to provide for a good sealing between the receptacle and the shell.

The provision of a proper sealing will be discussed in the following.

As already mentioned above, in connection with some embodiments, porcelain materials such as stoneware, earthenware, bone china, technical porcelain, high alumina porcelain and other porcelain materials can have a wide range of coefficients of thermal expansion (CTE). CTE of porcelain materials can vary in range of 3*10⁻⁶ 1/K to even 10*10⁻⁶ 1/K, whereas materials with an Al₂O₃ content of 75-99.99% exhibit a linear coefficient of thermal expansion of 6*10⁻⁶ 1/K to 8.5*10⁻⁶ 1/K. These two types of materials can be bonded together during firing with frit/glaze/glass or even can be co-fired together with for example a self-vitrifying porcelain.

However sometimes bonding porcelain (including stoneware, earthenware, bone china, high alumina porcelain, and other tri-axial porcelain materials) to the more heat conductive Al₂O₃ can be challenging if the coefficient of thermal expansion (CTE) differs too much. For example porcelain materials used in tableware industry can have linear coefficient of thermal expansion of 5*10⁻⁶ 1/K to 7*10⁻⁶ 1/K, whereas materials with an Al₂O₃ content of 95-99.99% have a linear coefficient of thermal expansion of 7.5*10⁻⁶ 1/K to 8.5*10⁻⁶ 1/K.

Directly bonding the two different materials with different CTEs without any modification to either the porcelain or Al₂O₃ materials can result in cracks or a non-durable bonding. Especially when the bonded objects are subjected to thermal shocks, for example pouring hot water in to the cup, or dropping a warm plate to cold water.

In case of thermal expansion mismatch for the selected porcelain material and Al₂O₃ grade, some methods can be used to reduce the stress and forces caused by thermal expansion mismatch.

Thus, in one embodiment, the above aim can be achieved by, for example, increasing or lowering thermal expansion of porcelain or by lowering thermal expansion of Al₂O₃.

In another embodiment, which can be combined with the previous, the frit/glaze/glass used for bonding can be selected so that the glass softening point is low, thus causing less stress during the cooling cycle in the kiln.

The frit/glaze/glass used for bonding is chosen because it best accommodates for thermal expansion coefficient mismatch.

To prevent cracking or improve durability of bonding Al₂O₃ to low expansion porcelain, the porcelain's thermal expansion coefficient is modified such that it is closer to Al₂O₃'s thermal expansion coefficient.

Porcelain material systems (for example stoneware, earthenware, bone china, high alumina porcelain, and other tri-axial porcelain materials) commonly can have 30-80% glassy phase after firing in the kiln.

When needed, it is possible to modify the thermal expansion coefficients of the materials used herein.

To take the embodiment, wherein the receptacle is manufactured from Al₂O₃ and the shell from porcelain:

Thus, for example, a high content of some metal oxides or certain fluxes or various mixtures of different compounds will increase the porcelain body's thermal expansion coefficient. Examples of compounds that can increase thermal expansion are Na, K, Ca, Fe, Zn, Ba containing inorganic or organic compounds, although this is no exhaustive list.

In addition, the thermal expansion coefficient of porcelain can be also raised by introducing high thermal expansion fillers such as quartz, cristobalite, leucite and alumina.

In case increasing porcelain thermal expansion is unfeasible, it is also possible to select a 75%-85% Al₂O₃ grade which has a lower thermal expansion coefficient than a material having a higher Al₂O₃ content. However, the 75%-85% Al₂O₃ grade can have lower thermal conductivity, which might limit the application. If both modifying thermal expansion of porcelain and using 75%-85% Al₂O₃ grade is unfeasible, one can use the above mentioned thermal expansion modified porcelain material or 75-85% Al₂O₃ as an intermediate bonding layer to accommodate CTE mismatch.

Example 1

Porcelain Body was Prepared Containing

Imerys Tableware PM410B porcelain 100%

Bisque fired to 900° C., and then glazed using Terracolor D8250a glaze. A 95% Al₂O₃ thin plate placed on top of the glazed porcelain body which was then fired to 1240° C.

After firing, many cracks originating from the 95% Al₂O₃ piece could be seen on the surface of the glaze.

Example 2

Porcelain body was prepared containing:

Imerys Tableware PM410B porcelain 96%

Potclays P 2275 frit 4%

Bisque fired to 900° C., and then glazed using Terracolor D8250a glaze. A 95% Al₂O₃ thin plate placed on top of the glazed porcelain body which was then fired to 1240° C.

After firing, no cracks on the surface of the glaze can be seen.

After heating the bonded porcelain-Al₂O₃ test specimen to 150° C. for 30 min, and then dropping it 20° C. water, many cracks originating from the Al₂O₃ piece could be seen on the surface of the glaze.

Example 3

Porcelain body was prepared containing:

Imerys Tableware PM410B porcelain 90%

Potclays P 2275 frit 10%

Bisque fired to 900° C., and then glazed using Terracolor D8250a glaze. A 95% Al₂O₃ thin plate was placed on top of the glazed porcelain body which was then fired to 1240° C.

After firing, no cracks on the surface of the glaze can be seen.

After heating the bonded porcelain-Al₂O₃ test specimen to 150° C. for 30 min, it was dropped into 20° C. water. No cracks on the surface of the glaze could be seen.

After heating the bonded porcelain-Al₂O₃ test specimen to 200° C. for 30 min, it was dropped in 20° C. water. No racks on the surface of the glaze can be seen.

Example 4

Porcelain body was prepared containing:

Imerys Tableware PM410B porcelain 80%

Potash Feldspar (K₂O>11.40% wt, Na₂O>2.70% wt) 12%

Quartz (Mesh 350) 8%

Bisque fired to 900° C., then glazed using Terracolor D8250a glaze and fired to 1240° C.

A 95% Al₂O₃ crucible was glazed using Terracolor D8250a with cellulose gum (0.5% wt) as glaze adhesive agent and fired to 1240° C.

Then, a thin layer of Potterycrafts P 2961 frit was applied on top of glazed porcelain body and the glazed 95% Al₂O₃ crucible, then the 95% Al₂O₃ crucible was placed on top of the porcelain and fired to 1000 C.

After firing, no cracks on the surface of the glaze or frit could be seen.

After heating the frit bonded porcelain-Al₂O₃ test specimen to 150° C. for 30 min, and then dropping it in 20° C. water, no cracks on the surface of the glaze or frit could be seen.

It is to be understood that the embodiments of the invention disclosed are not limited to the particular structures, process steps, or materials disclosed herein, but are extended to equivalents thereof as would be recognized by those ordinarily skilled in the relevant arts. It should also be understood that terminology employed herein is used for the purpose of describing particular embodiments only and is not intended to be limiting.

Reference throughout this specification to “one embodiment” or “an embodiment” means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, appearances of the phrases “in one embodiment” or “in an embodiment” in various places throughout this specification are not necessarily all referring to the same embodiment.

As used herein, a plurality of items, structural elements, compositional elements, and/or materials may be presented in a common list for convenience. However, these lists should be construed as though each member of the list is individually identified as a separate and unique member. Thus, no individual member of such list should be construed as a de facto equivalent of any other member of the same list solely based on their presentation in a common group without indications to the contrary. In addition, various embodiments and example of the present invention may be referred to herein along with alternatives for the various components thereof. It is understood that such embodiments, examples, and alternatives are not to be construed as de facto equivalents of one another, but are to be considered as separate and autonomous representations of the present invention.

Furthermore, the described features, structures, or characteristics may be combined in any suitable manner in one or more embodiments. In the following description, numerous specific details are provided, such as examples of lengths, widths, shapes, etc., to provide a thorough understanding of embodiments of the invention. One skilled in the relevant art will recognize, however, that the invention can be practiced without one or more of the specific details, or with other methods, components, materials, etc. In other instances, well-known structures, materials, or operations are not shown or described in detail to avoid obscuring aspects of the invention.

While the forgoing examples are illustrative of the principles of the present invention in one or more particular applications, it will be apparent to those of ordinary skill in the art that numerous modifications in form, usage and details of implementation can be made without the exercise of inventive faculty, and without departing from the principles and concepts of the invention. Accordingly, it is not intended that the invention be limited, except as by the claims set forth below.

The verbs “to comprise” and “to include” are used in this document as open limitations that neither exclude nor require the existence of also un-recited features. The features recited in depending claims are mutually freely combinable unless otherwise explicitly stated. Furthermore, it is to be understood that the use of “a” or “an”, i.e. a singular form, throughout this document does not exclude a plurality.

INDUSTRIAL APPLICABILITY

The present invention is suitable for any application requiring the rapid lowering or increasing of the temperature of a foodstuff, such as a liquid, or for cooling a foodstuff to a temperature below the ambient in a container and then maintaining the temperature of the liquid for an extended period of time. Among other things, the invention can be applied to drinking mugs or cups, baby bottles, carafes, and also for containing liquid for example in bathing tubs.

REFERENCE SIGNS LIST

-   1, 11, 21 Bottom -   2, 12, 22 Phase change material -   3, 13 Elasticity zone -   4, 14, 24 Receptacle -   5, 15, 25 Shell -   16 Holder for phase change material -   17 Non-ceramic outer shell

CITATION LIST Patent Literature

U.S. Pat. No. 2,876,634 A U.S. Pat. No. 7,934,537 B2 

1. An article for holding foodstuff, comprising: a receptacle having a wall with an inner surface for holding the foodstuff and an opposite outer surface, the wall being at least partially formed of a first ceramic material having a first thermal conductivity to allow for heat transfer through the wall; a shell spaced apart from the outer surface of the receptacle such as to define an interstitial chamber between the shell and the outer surface of the receptacle, the shell being at least partially formed of a ceramic material having a second thermal conductivity; and a phase change material disposed within the interstitial chamber and abutting at least the outer surface of the wall of the receptacle; wherein said first thermal conductivity greater than the second thermal conductivity.
 2. The article according to claim 1, comprising a vessel primarily for containing liquids, in particular aqueous liquids, such as a cup, a bowl or bottle, or an article primarily for holding non-liquid foodstuff, such as a saucer, plate, platter or bowl.
 3. The article according to claim 2, wherein the receptacle has an open upper end and closed lower end, wherein the wall interconnects the upper and the lower ends of the receptacle, so as to define a volume.
 4. The article according to claim 1, wherein the shell at least partially laterally surrounds the wall of the receptacle.
 5. The article according to claim 1, comprising a plate with inclined edges for holding aqueous foodstuff, or an at least essentially flat plate as a heat-accumulating mat or coaster.
 6. The article according to claim 1, wherein the wall of the receptacle has first edge portions defining the perimeter of the wall, and the shell has second edge portions defining the perimeter of the shell, said first and second edge portions being bonded together.
 7. The article according to claim 1, wherein the receptacle is made from a material selected from the group of ceramics, metal oxides and metalloid oxides and combinations thereof, for example Al₂O₃, in particular an Al₂O₃ grade having an Al₂O₃ content of 75 to 100% by weight.
 8. The article according to claim 1, wherein the ceramic material of the shell is a heat insulating silicate material, in particular a metal silicate material.
 9. The article according to claim 1, wherein the shell consists essentially of ceramic material.
 10. The article according to claim 1, wherein the shell comprises a ceramic material which laterally surrounds the wall of the receptacle and a polymeric material which forms the bottom of the vessel and which is placed on the opposite side to the lower end of the receptacle.
 11. The article according to claim 10, wherein the polymeric material which forms the bottom of the vessel is selected from the group of thermoplastic materials, silicone and elastomeric materials.
 12. The article according to claim 1, wherein the wall of the receptacle is sealed to or against the shell.
 13. The article according to claim 12, wherein the ceramic material of the inner layer is bonded to the ceramic material of the shell by co-firing, fit bonding or glass or glaze bonding of ceramics.
 14. The article according to claim 1, comprising an elasticity zone disposed within the interstitial chamber on the opposite side of the phase change material with respect to the outer surface of the wall to allow for expansion and contraction of the phase change material within the interstitial chamber under the influence of thermal energy.
 15. The article according to claim 14, wherein the elasticity zone separates at least a significant portion of the shell and the phase change material.
 16. The article according to claim 14, wherein the elasticity zone comprises a silicone, an elastomer or a thermoplastic material.
 17. The article according to claim 14, wherein the elasticity zone comprises a gas-filled space.
 18. The use of an article according to claim 1 for holding liquids, such as beverages, in particular hot or cold beverages. 